The invention relates to a discharged lamp, and more particularly, to a discharge lamp wherein its base contacts are connected in each case to an electrically conductive spring element. Each spring element bears against the wall of the at least one tubular lamp vessel and making an electric contact between in each case one section, arranged outside the lamp vessel, of a lamp electrode and a base contact. The spring elements ensure reliable electric contact between the base contacts and the electrode sections arranged outside the lamp vessel, and simple provision of a base for the discharge lamp.
Such a discharge lamp is disclosed, for example, in German patent DE 197 18 395 C1. This patent describes a fluorescent lamp with a tubular discharge vessel and an enclosed inert gas. This lamp has elongated electrodes which run parallel to the longitudinal axis of the lamp and serve to produce a gas discharge. At least one of these electrodes has a section with is lead out of the interior of the discharge vessel, is developed as a supply lead and is fitted on the inner wall of the tubular discharge vessel. The lamp base is equipped with two contact pins which in each case are connected in an electrically conducting fashion to one of the lamp electrodes.
It is the object of the invention to provide a base for a discharge lamp of the generic type which ensures reliable electric contact is made between the electrodes and the base contacts.
This object is achieved according to the invention by means of the characterizing features of patent claim 1. Particularly advantageous designs of the invention are described in the subclaims.
The discharge lamp according to the invention is distinguished from a discharge lamp of the generic type in that its base contacts are connected in each case to an electrically conductive spring element, each spring element bearing against the wall of the at least one tubular lamp vessel and making an electric contact between in each case one section, arranged outside the lamp vessel, of a lamp electrode and a base contact. The spring elements ensure reliable electric contact between the base contacts and the electrode sections arranged outside the lamp vessel, and simple provision of a base for the discharge lamp.
The spring elements are advantageously constructed as leaf springs with cambered ends, the cambered leaf spring ends in each case making electric contact with one of the aforementioned electrode sections. The cambers ensure a sufficiently large contact surface between the leaf springs and the electrode sections, and prevent damage to the surface of the electrode sections. Moreover, the leaf springs are advantageously provided in each case with at least one expansion loop by means of which account is taken of the different coefficients of thermal expansion of the lamp vessel and the leaf springs. In order to ensure a particularly reliable electric and mechanical contact is made, the spring elements are advantageously connected in each case to the corresponding electrode section by means of a soldered joint. By contrast with a welded joint, the soldered joint has the advantage that, given a base shell plugged on the lamp vessel, it can be produced by inducing heating of the base contacts by radio frequency, when the electrode sections, arranged outside the at least one lamp vessel, or the spring elements have had soldering paste applied or have been tinned.
The electrode sections constructed as supply leads are advantageously fitted on the inner wall of the at least one tubular lamp vessel, and the spring elements therefore bear against the inner wall of the lamp vessel and make mechanical and electric contact with these electrode sections. As a result, the electrode sections and also the spring elements can be better protected against damage and being touched.
In accordance with a preferred exemplary embodiment of the invention, a first end of the at least one lamp vessel is equipped with a base shell which is provided as a component of the lamp base with the at least two base contacts, the base contacts being connected in each case to an electrode section lead out of the first end of the at least one lamp vessel. Consequently, in the case of the preferred exemplary embodiment the electrodes are supplied with power exclusively via the first end of the at least one lamp vessel. It is therefore sufficient in this case to provide the discharge lamp with a base at only one end, or else to provide the other end of the at least one lamp vessel with a base shell without electric contacts which serves only to hold the lamp in a lampholder. However, it is also possible to provide both ends of the at least one lamp vessel with base shells which have electric contacts. In this case, there is lead out of both ends of the at least one lamp vessel at least one electrode section which is constructed as a supply lead, bears against the inner wall of the at least one tubular lamp vessel and is connected to a base contact.
The base shell or the base shells of the lamp base advantageously consist of an electrically insulating, thermoplastic material. This permits the base shell or the base shells to be fused to the ends of the at least one lamp vessel. The lamp base advantageously has at least one base shell with a cup-like receptacle for an end of the at least one lamp base, whose diameter is coordinated with the outside diameter of the corresponding end, and in which the spring elements are arranged. The cup-like receptacle firstly offers the spring elements adequate protection against damage and being touched, and secondly permits the spring elements to be positioned accurately relatively to the corresponding end of the at least one lamp vessel and to the electrode sections fitted on the inner wall and constructed as supply leads. Each base shell advantageously has a means capable of being heated by radio-frequency induction and is arranged in each case in an annular groove surrounding the receptacle of the corresponding base shell. These means can be heated by radio-frequency induced voltage pulses such that the thermoplastic material of the base shell fuses in the region of the groove and, after hardening, forms a fused connection with the at least one lamp vessel. An electrically insulating means can be arranged with advantage between the spring elements arranged in the same receptacle.